No abstract

We have examined the durability of oxygen and hydrogen electrodes for reversible solid oxide cells (R-SOCs). The use of a dense, uniform samaria-doped ceria (SDC) interlayer was very important to obtain high performance and high durability of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) -SDC composite oxygen electrode. Double-layer hydrogen electrodes, consisting of SDC scaffold with highly dispersed Ni-Co nanoparticles as the catalyst layer (CL) and a thin current collecting layer (CCL) of either Ni-SDC or Ni-YSZ cermet, exhibited nearly identical initial performance at 800°C, while the use of Ni-YSZ CCL together with threedimensional network of Ni in the CL resulted in higher durability.

We have developed high performance electrodes for reversible SOEC/SOFCs. Double-layer hydrogen electrodes, consisting of a mixed conducting samaria-doped ceria (SDC) with highly dispersed Ni–Co catalysts as the catalyst layer (CL) and, on top of it, a thin Ni–SDC cermet as the current collecting layer (CCL), exhibited highly reversible performance at 800°C by controlling the microstructure. We have also succeeded in enhancing the reversible performances of LSCF–SDC composite oxygen electrodes accompanied by high durability.

We have examined the long-term durability of a La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3¹¤ (LSCF)samaria-doped ceria (SDC) composite oxygen electrode with SDC interlayer for reversible solid oxide cells (R-SOCs). A symmetrical cell with the configuration: LSCF SDC«SDC interlayer«yttria-stabilized zirconia (YSZ) electrolyte«SDC interlayer«LSCFSDC, was operated at 900°C and a constant current density of 0.5 A cm ¹2 with the top electrode as the anode (O 2 evolution). The IR-free overpotentials at both the anode and cathode were virtually constant during 5500 h of operation. The value of ohmic resistance at the anode side (R A ) increased slightly, whereas that at the cathode side (R C ) increased markedly. The IE performance of the bottom electrode (operated as the cathode), that was measured from ¹1.0 to 1.0 A cm ¹2 every 1000 h, degraded specifically at high current densities. It was found that the thickness, pore size, and porosity in both electrodes were unchanged, but the distribution of the Sr component changed markedly at both the LSCFSDC/SDC interlayer and SDC interlayer/YSZ interfaces. While the diffusion of the Sr component from the anode was limited within the SDC interlayer, the Sr component from the cathode reached the SDC interlayer/YSZ interface, which could increase the R C , likely due to the formation of SrZrO 3 . However, the diffusion rates of Sr were found to be noticeably slowed down at dense portions of the SDC interlayer. Hence, it is essential to prepare a dense, uniform SDC interlayer to improve both the durability and performance of R-SOCs.